Accumulators are used in manufacturing systems, and particularly paper processing systems, to store elongated logs of product that have been formed into elongated rolls or stacks prior to being reduced in length for commercial packaging. For example, during formation of interfolded paper towels, the paper towels are initially formed into an elongated stack of interfolded paper towels that can be in excess of eight feet long. This log is then passed to downstream processing systems to be sawed into shorter lengths, such as twelve (12) to eighteen (18) inch lengths for example. These shorter lengths are then packaged for consumer use.
The accumulators store the logs as they are dispensed from the system that forms the logs in the event that there is a breakdown, scheduled maintenance, or other downtime experienced by either the upstream or a downstream system. The accumulator allows the other system that is not experiencing downtime to continue to operate. This can be very beneficial in the event that either system needs to run continuously to avoid long reset or startup time.
One problem particularly occurs with the use of rectangular logs of stacked paper. These logs do not roll. As such, they have to be slid laterally into buckets of the accumulator by a feed arrangement. The feed arrangement includes a pusher element that pushes the logs laterally into the buckets in a direction that is generally perpendicular to the direction of travel of the buckets. Thus, the bucket and the feed arrangement must be aligned during the process of loading a log into the bucket.
Further, logs of stacked paper products are typically void of any central core, such as in wound products like rolls of paper towels or toilet paper. The lack of a central core can reduce the rigidity of the log such that the log should be supported substantially along its entire length and not merely at the ends thereof.
By requiring a pusher element to push the logs into the buckets, the buckets and the feed arrangement need to be maintained at a constant relative position during the loading operation to prevent damaging the logs or otherwise prevent interference between the components of the buckets and the feed arrangement.
To store the logs in a space efficient manner, the accumulator typically includes a transport system that includes an endless carrier arrangement, e.g. a pair of parallel chains, that transports the buckets vertically up and down repeatedly. The buckets change vertical direction, typically, as the chains rotate about sprockets. Unfortunately, due to the change in direction, the buckets will tend to start to swing due to the acceleration/deceleration of buckets.
In the past, the entire system of buckets was stopped while an individual bucket was loaded. The system was then indexed to the next bucket for loading and then stopped again. However, the acceleration and deceleration of the system due to stopping and starting of the system amplifies the magnitude of the swinging of the buckets.
If the magnitude of the swinging is too severe, the swinging buckets can cause damage to the accumulator or cause the product to be spilled from the buckets.
As a result of above, the speed/throughput of prior accumulators has been limited. Modern upstream/downstream equipment could operate at higher speeds if accumulator speed could be similarly increased.
In prior approaches, however, running the accumulator at higher speed to increase throughput of logs through the accumulator by merely increasing speed of the chain through the accumulator will increase the acceleration/deceleration of the buckets as they traverse the changes in direction. This will thus result in increased swinging. This amplified swinging is then amplified again by the acceleration and deceleration of the system during the loading process. Further, as the chains must be accelerated to the now faster speeds, the magnitude of acceleration or period of acceleration from a dead stop to top speed must be increased further amplifying the swinging problem.
The present invention provides improvements over the art that permits faster throughput through an accumulator while preventing or reducing increases in swinging magnitude of the buckets.